A trunking communication system emerged in late 1970s and early 1980s. The earliest trunking communication is a simulation system. Digital trunking technology realized worldwide presence in 1990s. In late 1990s, digital trunking network appeared in China. The trunking communication service may include a plurality of users one time. These users are allocated to different groups according to their belongingness and one group is called a trunking group. One of the most prominent features of trunking communication is a massive call or group call. The group call function of trunking service refers to that: calling a group number at a communication terminal or a dispatcher station may bring all terminals in the group into a call, thereby realizing the effect of multi-person concurrent call.
The trunking communication system conventionally uses a group call ID to identify a trunking group. A group call ID uniquely identifies a trunking group, and typically may consist of a Group Identification (GID or Gid) (or called group identity) alone or as well as other attributes like group call area. Wherein, the GID identifies the terminals in the trunking group. All terminals in this trunking group have the GID defined by this trunking group. The trunking group stores its GID in a data memory device at the system side and in terminals, and uses the GID to determine the trunking group where this terminal is located during an authentication. One terminal may subscribe a plurality of trunking groups in the same time. The group call area refers to the area in which this trunking group may call when the group call of the trunking group is a voice group call service. Only the terminals which are located in this area and are members of this trunking group are available to the call service. As the GID is used to identify the trunking group to which the terminals belong, different trunking groups have different GIDs. However, the GID resources are limited. For example, if a GID number has three digits, 1000 trunking groups can be identified; if a GID number has four digits, 10000 trunking groups can be identified. With the continuous expansion of trunking networks, this GID encoding method is far from enough for the trunking communication system in a whole communication network. Moreover, to adapt to the development of the trunking communication system by using this GID encoding method and increasing digits of the GID will cause inconvenience in management.